Protective device for electrical devices



March 17, 1931. I. H. VAN HORN ET AL 1,797,031

PROTECTIVE DEVICE FOR ELECTRICAL DEVICES Filed March 4, 1924 fNyEN TUE5: IRYJNE- 'X/ANHURN, WZ'LBUR. A. PIFZTIIZ,

THEIJL'L ATTURZSZE Y.

patented Mar. 17, 1931 V UNITED STATES PATENT OFFICE name a. van normAnn WILBUB A. PIPKIN, or EAST CLEVELAND, onro, ASSIGNORS To GENERALELECTRIC COMPANY, A CORPORATION OF'NEW xonx PROTEUIIV'E DEVICE FORELECTRICAL DEVICES Application filed l Iarch 4,

Our invention relates to protective devices for electric incandescentlamps and other electric lamps and devices which comprise an electricenergy translating device such as a filament sealed in a glass bulb, andmore particularly to such lamps which are provided with an axiallydepending rod or tube such as the exhaust tube comprised by incandescentlamps made according to the tipless lamp process disclosed in Mitchelland White Patent 1,423,956. According to our invention, the protectivedevice is in the form of a ring or disc having an aperture in the centerportion thereof. This allows the protective device to be veryconveniently disposed about the end of the exhaust tube .or other glassrodcarried by the lamp or other device. As a specific embodiment of ourinvention, we disclose herein an improved fuse, but it will beunderstood that our inventionis of such scope that it relates to otherprotective devices which are used in connection with incandescentelectric lamps and similar devices. n i 25 According to a specificembodiment of our invention we rovide a fuse consisting of a Conductingwlre whose resistance is high compared with that of the rest of thefilament circuit connections or portions thereof. This conductor is verysmall in diameter which lends to the quickness with which the circuit isbroken by the abnormal current. The said conductor is surrounded with aninsulating material strong enough to resist bursting when the fuse isblown. We prefer to utilize a material which has the requisite strengthwithout being too 'cumbrous. This is especially true when it is desiredto in corporate the fuse within the incandescent lamp or otherelectrical device. One material which we have found to be quite suitableis finely divided zirconium silicate to which is added sodium silicatesolution of a specific gravity of about 1.4 to form a paste which can bereadily molded. Upon drying this roduces'a-very strong insulatingcovering or the fuse wire. For the fuse wire we prefer to usecomparatively high resistance wire. We have found that the low expansioncopper-clad nickel iron wire which is cus- 1924. Serial No. 696,898.-

tomarily used as the sealing in portion of leading-in conductors forelectric incandescent lamps is satisfactory for this purpose. Thiscombination of insulating material and fusewire makes a fuse which doesnot burst when blown. Moreover, the insulating coating adheres very,strongly to the wire and this prevents blowing out at the ends. It isobvious that there are other materials which may be substituted for thezirconium silicate w and sodium silicate to form a suitable insulatingcoating as the principal requisite is high mechanical strength. Othermetals may be substituted for the copper clad nickel iron wire. Theprincipal requisite is that as the wire shall have comparatively highresistance and will blow before the wire in the stem press.

In the accompanying drawing Fig. 1 shows our invention applied to anelectric incandescent lamp of the type disclosed in the Langmuir PatentNo. 1,180,159; Fig. 2 is a plan view of the protective device andconductors connected thereto; and Fig. 3 is a horizontal 7 sectionthereof.

' The incandescent lamp shown in Fig. 1 comprises the bulb 10 into whichis sealed the hollow glass stem 11 through which extend the leading-inwires 12 13 which comprise portions 14 15 consisting ordinarily of socopper-clad nickel-iron wire having the proper coeflicient of expansionto form a seal with the compressed end .ortion 16 of the stem. The innerportions 1 18 of these leading-in wires are connected to the filament 19which is suitably supported through the wires 20 whose ends areembeddedin the glass arbor 21 extending from the stem press 16. Anexhaust tube 22 is'located within the hollow stem 11 and has its outersealed end project- ,ing slightly beyond the said stem. Said lampcomprisesthe usual base 23 to the shell of which the conductor 12 isunited and to the center Contact 24 of which the other leadinginconductor 13 is united.

According to our invention there is comprised in the electric circuitand connected to the leading-in conductor 13 a fuse 25. As shown in Fig.3, the said fuse comprises a wire 26 which is preferably of the copper-100 1 conductors. However, its resistance is highbody, and a stem havinga rod extending lon- 'gitudinally within the same and leading-in erwhich may be accomplished by making it longer or thinner than theportions 14 or 15.

Surrounding the said conductor is an insulating jacket 27. The materialused for this jacket is made by mixing finely divided zirconium silicatewith a sodium silicate solution of about 1.4 specific gravity to form apaste which may be shaped as is desired.

around the conductor 26.

Upon the breaking of the filament 19 durand mounted within said base andsurround ing the end of said exhaust tube.

In witness whereof we have hereunto set our hands this 29th day ofFebruary, 1924. IRVING H. VAN HORN. WILBUR A. PIPKI N.

ing the use of the incandescent lamp an are ordinarily springs betweenthe conductors 17 18. This will gradually fuse them down.

,The increase in current consequent. upon the springing of the arc willblow the fuse 25 before the arc has reached the stem press and thusavoid explosion of the lamp which frequently occurs if the arc travelsthrough the stem press.

What we claim as new and desire to secure by Letters Patent of theUnited States, is:

1.' In an electrical device, the combination of a glass container, abase, a mount comprising an energy translating body, a stem sealed tosaid container having an exhaust tube extending longitudinally withinthe same and leading-in wires sealed in said stem, of a ringshaped fusein series withorle of said leading-in conductors and mounted at theouter end of said stem so as to be enclosed by said container and baseand so as to surround said exhaust tube. V

2. In an electrical device, the combinatio of a glass container and amount comprising a hollow stem sealed to said container, an energytranslating device mounted thereon, leading-in conductors sealed in saidstem and connected with said energy translating device-and an exhausttube extending through said stem, a disc-shaped fuse in series with oneof said leading-in conductors mounted at the end of said stem andperforated to pass ovler and surround the end of said exhaust tu e.

3. In an electrical device, the combination of a glass container havingsealed therein a mount comprising an energy translating wires sealed insaid stem, a base and a rin shaped protective device electrically conneced with said leading-in wires and mounted within said base andsurrounding the end of said rod.

4. In an electrical device, the combination of a glass container havingsealed therein a mount comprising an energy translating body, and a stemhaving an exhaust tube extending longitudinally within the same andleading-in wires sealed in said stem, a; base and a rmg-sha edproteotivedevice electrically connecte wlth said leading-in wires

